Ringing arrangement for electronic switching systems



Dec. 27, 1949 D. H. RANSOM 2,492,180

RINGING ARRANGEMENT FOR ELECTRONIC SWITCHING SYSTEMS Filed April 26, 1947 s Sheets-Sheet 1 MASTER DNWER RNGJNG PHASED.

INVENTOR. v DAV/D )P/IMSOM ATTORNEY Dec. 27, 1949 D. H. RANSOM 4 2,492,180

RINGING ARRANGEMENT FOR ELECTRONIC SWITCHING SYSTEMS Filed April 26, 1947 3 Sheets-Sheet 2 PHASE (.ORRECTOR CLWPER i; /D\FFERENT\A- C9 me cnzcun 73 SYNCHRONZED MULTVVIBRATOR L W PASS GMN 65 'IE CONTROL l I 42 5 g U INVENTOR.

A TTOFNEY Dec. 27, 1949 4 D. H. RANsoM/ RINGING ARRANGEMENT FOR ELECTRONIC SWITCHING SYSTEMS s Sheets-Sheet 3 Filed April 26, 1947 PU LSE SH APlNG MPUHER T PULSE SHAPING AMPUHER INVENTOR. DAV/0 l1. IBM 50M I ATTOii/E? Patented Dec. 27, 1949 RINGING ARRANGEMENT FOR ELECTRONIC SWITCHING SYSTEMS David H. Ransom, London, England, assignor to Federal Telecommunication Laboratories, Inc., New York, N. Y., a corporation of Delaware Application April 26, 1947, Serial No. 744,112

1 12 Claims.

This invention relates to new and useful improvements in telecommunication systems, and more particularly to electronically controlled systems of the type disclosed in my application, Serial No. 643,285, filed January 25, 1946.

It is the object of the present invention to provide a completely electronically controlled ringing iarrangement for telephone systems of the above The nature of the invention will more clearly appear from the appended claims and the following detailed description of an embodiment thereof. The drawings show diagrammatically as much of a telephone system as is necessary for an understanding of the invention.

Fig. 1 shows part of a subscribers line circuit and the central exchange equipment common to a. group of subscribers lines, as well as the central exchange dial pulse responsive and ringing control equipment.

Fig. 2 illustrates the line finder and the talking circuit associated with a link, and

Fig. 3, the register and called line selector provided for a link.

When a subscriber desires to initiate a call, the operation of the switch-hook at his station. places a negative potential on the dynode of the calling line in distributor I. This will cause the flow of electrons from the dynode to the anode whenever the dynode is scanned by the cathode ray beam of the distributor I The negative pulse from the anode is fed to a cathode follower and inverter 2 whose cathode output is. fedto a clipper amplifier 3. The amplifier 3 .is biased to draw current normally wherebyeach negative. pulse will drive it beyond cut-off, clipping any variation due to transmitter modulations or dial pulses. The plate output of tube 3 is fed to a cathode follower 4 whose cathode is connected to the grids of all line finder gate tubes 5. The line finder gate tubes are normally biased-far enough beyond cut-oil so that the incoming signal will not aifect their plate output.

A lock-in oscillator 6 in each line finder oper-- ates at a frequency slightly less than the rate of, dynode scannin controlled by a 200-kc. master oscillator I. The output of lock-in oscillator 6 is divided to a frequency of approximately 50 kc. and is passed through a clipper amplifier and diflerentiating network 8 to a multivibrator arranged to synchronize at kc. The outputof the multivibrator 9 is differentiated in the grid circuit of a clipper tube ill. The constants and square wave of approximately five micro-seconds duration in the plate circuit of the tube from the leading. edge of the differentiated pulse and to suppress the trailing edge. The resulting negative pulse is passed through a cathode follower II to the cathode of the line finder gate tube 5. The amplitude of this pulse is adjusted by a delayed gain tube I 2 so that normally the line finder gate 5 remains cut-off. Neither signal will drive the line finder gate 5 beyond cut-off to conduction.

The frequency of the line finder lock-in oscillator 6 being slightly less than that of the master oscillator 1, these two pulses applied to the line finder gate 5 will drift in time until they occur simultaneously, whereupon gate will be opened to pass a signal on its plate to the integrating net and rectifier l3. A gate control tube l4 will be driven to cut-off after a few pulses, permitting a lock-in gate l5 to pass a signal from the master oscillator 1 through a phase corrector It to the lock-in oscillator B, synchronizing the latter.

A portion of the rectifier output of the line finder gate is fed to the grid of the delayed gain tube I2 which will be driven beyond cut-off after a few pulses. Since theplate resistor ll of the delayed gain tube is connected with the screen and clipper amplifier I 0, the screen voltage of the latter will rise and increase the amplitude of the pedestal pulse which is applied to the cathode of the line finder gate 5 whose grid will thus be driven positive by the incoming pulse from the common circuit, and clipping by grid current will occur. The signal amplitude of the incoming pulse will then be insufiicient to affect the line finder'gate in any other link.

The plate output of the line finder gate 5 is used to control the speech gates l8 and l9. i8 is normally biased to cut-off on its suppressor grid by the voltage drop in the plate resistor of a gate control tube 20. The negative pulse from the line finder gate 5 drives the grid of tube 25) beyond cut-01f, putting the suppressor grid of the input gate H3 at ground potential, permitting the passing of signals that arrive on the control grid of input gate l8.

It is assumed that speech and dial pulses will modulate the line signals at twenty-five percent and the clipping action of tube 3 will cut off modulated portions so that a uniform signal will be available for the line finder circuit. However,

lated portion of the positive pulses from the plate I bias of this tube are adjusted to form a short, of inverter 2 will appear in its plate circuit and in the cathode follower 22. The output of the latter is fed over conductor 23 to the control grids of the input gate tubes I8 of all the links.

Normally the dial pulse circuit receives a series of negative pulses from the input gate I8 which are interrupted by each dial pulse. The positive pulses appearing in the plate circuit of the input gate I8 are passed over a conductor 23, through a pulse stretching and integrating network 2%,

to the grid of an amplifier 25, and the amplified low frequency dial pulses thus produced are shaped in an amplifier and clipper tube 25 to form square wave pulses which are, in turn, differentiated in the network connected with the rid circuit of a dial gate tube 21. is biased so that the leading edge of the differentiated pulse will be suppressed and the trailing edge passed as a negative pulse over conductor 28 to the register circuits.

The register circuits are conventional Eccles- Jordan trigger circuits connected to form a strip count. Initially, the right-hand tube 253 of the No. 0 register and the left-hand tube 39 of the No. 1 register and of all subsequent registers are conducting. The first negative pulse will transfer conduction in the Not) register from triode 29 to triode 3|. The latter, in turn, will put a negative pulse from its plate to transfer conduetion in the No. 1 register from tube 30 to tube 32. The next pulse will repeat this sequence of operation in the No. l and No. 2 registers. After a series of pulses one register will remain conducting on its right-hand side which will bias the suppressor grid of the time channel gate tubes 33, '34, etc. 35 associated with this register, so that signals may be passed from the control grid thereof.

Referring now to the dial pulse circuit the leading edge of the first pulse will cause a flip-flop circuit, comprising tubes i315 and '37, to transfer conduction from 3"! to 35. This condition will be maintained throughout the series of pulses by the potential built up in a pulse stretcher and integrating network 38 connected with the grid of tube 3 6.

At the end. of the series of pulses, 3'! will again become conductive, sending a negative pulse to the rin ing gate control flip-flop circuit comprise ing tubes 35 and ill. Normally 39 is conducting, biasing over a conductor ll and suppressor grid of the dial gate 21 to pass si als. The negativepulse at the end of the series of pulses will flip conduction to st and app y a biasin po ential ver conductor to the c ntrol grid of a ringin gate 4.

supp essor rid oi the rin gate w ll be as y the ne a ive pulse utpiu of. gate control 44 which, under the control of the time hannel t is op ra d to pass signal during the called time channel, permitting, in turn, through the agency of gate G3 to pass ringing signals during this period from a ringing oscillator 45, over the conductor 42, the gate 43, a gain control circuit 45, conductor 1, to the grid of the distributor i. This signal will actuate a cold cathode gas relay at the called station to operate a visual or audible signal.

' When the called subscriber answers, pulses are generated on the common anode of the distributor tube I during the called line period and arepassed by the cathode follower 2, clipper 3 and output cathode follower over conductor 8, to the control grid of a trip gate 69. The suppressor grid of 49 is connected over conductor 59 with the plate output of talking gate control ss. If the negative pulse. thus applied to the suppressor This gate tube grid of trip gate 49 occurs at the same time as the positive pulse which is applied to its control grid over 48, then the trip gate will send a negative pulse over conductor 5| to the ringing gate control to fiip conduction back to tube 39. This will cut on" the ringing gate 43 and flip conduction in a talking gate control flip-flop circuit from a triode 52 to a triode 53. ,A pulse is now applied over conductor 55 to the control grid of talking output gate control It and will bias it to conduction.

--'I-he ime selecting circuit (Fig. 3) counts the rlinierenoe pulses set in the register on a counting circuit, synchronizing on each count with apulse iromthe line finder gate 5 over conductor and'a pulse shaping amplifier 55. Normally the left-hand tubes of the counters, i. e. tubes 58, .etc., are conducting, and the synchronizing. negative pulse will flip conduction to the right-hand tubes of the counters, such as 59, 60, etc. Negative pulses derived at fivemicro-second intervals from the master oscillator l in the common circuit are passed over conductors SI, 62 through a pulse shaping amplifier E3, and are fed to the grids of all theright-hand counters '59, 69, etc. The next pulse atter the synchronizing pulse will transfer conduction in the No. 0 counter from 519 $0 51, whereupon a negative pulse is sent from the plate of 5 to the grid of 58 in the No. 1 counter, flipping conduction to 69. Each successive pulse will flip a counter so as to make the right-hand tube conducting until all the counters are operated, the final pulse of the series restoring the circuit to normal. Thus, for the period .of a count corresponding to the operated register, the. grid .of the gate tube for the pair will be made positive and the pulse will be fed to the gate control tubes by the associated time gate over conductor 154 to the control grids of the gate control tubes 44 and 2|] in parallel. For example, if the No. l re ister is conducting on its right hand tubes 32, then the positive bias on it is transferred to the suppressor grid tothe-No. 1 time channel gate 33, so that when in the No. 1 counter conduction flipped to the .righthand tube St, a negativev pulse will be generated on. the plate .of 3.3 and passed, as above stated, over the conductor 54 to the control grids .ofv 2D and 44.

The circuit is now ready to pass speech signals from th appropr ate dynode of distributor I to cathod follower and inverter 2, clipper 2 I, cathode follower 22, conductor 23 and the control grid of input gate I8. This gate is opened by pulses from the gate control 20 which is opened not only by pulses applied. thereto by the time channel gate 33 when the beam of the distributor I engages the dynode of the called line, but also by pulses applied thereto from the output circuit of line finder gate 5 when the beam of the distributor I sweeps over the dynode of the calling line. The signal from the plate of input gate I8 is fed over a low pass filter 55 where it is converted' to the original speech and, thence, to the control grid of the output gate IS. The output gate is opened by the signal from the line selector circuit conveyed thereto via gate control 44 and corresponding, therefore, to the time period of the called line. The plate of the gate control i9 is connected as the plate of the ringing gate 43 over gain control 46 and conductor 7 with the grid of the distributor I as the beam sweeps the called line where it is passed through a low pass filter to the called subscribers telephone set.

Speech in the opposite direction passesthrough ammo thesame patln except that. the timing of the input gate 18 is under the control. of the line selecting circuit (Fig. 3) and the output gate 13 is under thev control of the linev finder circuit. Since there is a feedback path in. this. circuit to each terminal, the gain control circuit. M5 is provided. to. insure that the. gainv around the system will always be less than unity..

The. called line cannotv be. selected by a line finder when the receiver is. removed from the hook, oi the telephone. set at the called station, becausethe pulsesfrom theoperated' time channel gate 13, 34,. etc. are. fed. over a conductor 66 and a bu y pulse shaping, amplifier B1 to. the grid of a busy gate 68. This. tube will place a negative pulse on the grids. of all the line finders which will neutralize the positive line pulse- When the calling subscribed hangs up, the circult releases under the control of the delayed gain tube 12; through the agency of a release control flip-flop circuit comprising triodes B9 and 10 and a release tube 1 I. At the start of the. call, the delayed gain tube it is driven to cut-off, lowering the potential on the control grid of 10. This will transfer conduction from 69 to 10, sending a negative-pulse to 'H which is biased beyond cutcfi and has, therefore, no effect; When, however, the line-finder releases, then 69 in the release control circuit again becomes conductive and sends a positive pulse to- H which transmits a negative pulse over conductor 12 torestore the operated register and the dial gate control to normal.

The circuit is now ready for the next call.

What I claim is:

1. In a communication system, a plurality of lines, an electronic. means; common to said lines and having a plurality of electrodes in which the. lines terminate, a control grid, and means for cyclically sweeping with an electron beam the electrodes to establish connection therewith, a. signal repeater having an output. connected. with said control grid. to vary therethrough the intensity of the beam. in. accordance: with signals, a. source of signaling potentials, timing means for applying to the repeater signals originating on calling and called lines when the beam of said electronic means sweeps over their terminals, and timing means for applying to the repeater signals from said source when the beam of said electronic means sweeps over the called line terminal.

2. The system according to claim 1, and in which the electronic means comprises a cathode ray tube.

3. The system according to claim 1, in which the signal repeater comprises two discharge tubes having input and output circuits, means for effectively associating the input circuit of one tube with the electrodes of the calling and called lines when they are swept by the beam, means for associating the input circuit of the other tube with said source when the terminal of the called line is swept by the beam, and means for effectively associating the output circuits of both tubes with the control grid when the beam sweeps the electrodes of the calling and called lines.

4. The system according to claim 1, a plurality of signal repeaters, each having a source of signaling potentials, means operative upon the initiation of a call for taking into use one of said repeaters, means for disconnecting the source from the repeater when the called line answers, and means for releasingthe repeater taken into use upon the termination of the call.

5. In a communication system, a plurality of lines, electronic means having means for moving a beam of electrons, a. control grid for the beam and; a plurality of electrodes in. which said lines terminate, means. for operating said electronic means. continuously and cyclically to sweep said terminals with its beam, a plurality of normally inactive. link, a signal input tube and pairs of. signal output tubesin each link, input, output and controlcircuits for the. tubes, a source of signaling potentials in each link, means operative upon the initiation of a call on a line for selecting: a link, means for operating the control circuit of the first output tube in the. selected link. when. the beam sweeps the electrode in which the called line terminates. and inefiective at all other times, means. for operating thecontrol circuits to render effective the input. and the second output. tube in the selected link when the beamsweeps the electrodes in which the calling and called lines termi nate and ineffective at all other times, aconnection from the output of the input tube to the input of the second output tube, means for associating the input of'the input. tube with the electrodes inwhich the calling and called lines terminate when they are swept by the beam, means for associating, the input of the first output tube with said source when the called line terminal is swept by the beam, and means for connecting the output. of.

both output tubes with the control grid when the.

electrodes of the calling and called lines are swept bythe beam.

6. The system according to claim 5, in which each link has a normally inactive line finder gate tube and called time-channel selector gate, means for actuating said line finder' gate tube upon the initiationofacall, means for operating the line:

finder gate tube toconvey signals from the calling and called lines to the signal inputtube when-- ever the electron beam sweeps over. the terminatingelectrodes thereof, and means for operating. the selector ate tube to convey signals to both output tubes when the electron beam sweeps over. the terminating electrode of the called line.

'7: A- system for interconnecting two channels of diiferent time displacement for two-way energy transfer between said channels, comprising a first means for receiving energy from either channel, a second means for applying energy to either channel, means for transferring energy from said first to the second means, selectively operable means for producin a time displacement of the energy received from one channel equal to the difference in time displacement between said channels, line finder means responsive to energy received from a channel, a source of signaling potential associated with said selectively operable means, a third means for transferring energy from said source to said second means, means jointly controlled by said line finder and selectively operable means for alternately operating said first means under the control of both channels, and means controlled by said selectively operable means for effecting energy transfer from said source under the control of one channel.

8. The system according to claim '7, and in which said first, second and third means are normally ineffective vacuum tubes, means jointly controlled by the line finder and selectively operable means for alternately rendering the first and second tubes effective, and means controlled by the selectively operable means for rendering the third tube efiective.

9. A telephone system for interconnecting calling with called channels of different time displacement for two-way speech over said channels, comprising a speech input tube for receiving energy from the calling and called channel, a speech output tube for applying energy to the calling and called channel, a source of signaling potential, a signal output tube operated by said source, a connection for operating the speech output tube in accordance with the operation of the input tube, selectively operable means for producing a time displacement of the energy received from one channel equal to the difierence intime displacement between said calling and called channels, line finder means responsive to, energy received from a channel, means jointly controlled by said line finder and selectively operable 'means for alternately rendering effective said input and signal output means, and means controlled by the selectively operablemeans for rendering efi'ective the signal output tube only during the called channel.

10; The system according to claim 9, and means controlled over the called channel for rendering ineffective the signal output tube.

1.1. In a telephone exchange system, a cathode ray tube having a control grid and a plurality of dynodes, means for continuously rotating the beam of said tube successively to engage said dynodes, a telephone line connected with each dynode, a speech input, a speech output and a ringing gate tube each having a cathode, an anode, a control grid and a suppressor grid, the three gate tubes being common to all telephone lines, a connection from the control grid of the cathode ray tube to the anodes of the output and ringing gate tubes, gain control means in said connection to keep the total gain around the system at less than unity, a connection for applying potentials to the control grid of the input gate tube through the dynodes of the calling and the called line, two triodes common to said lines, one for applying potentials to the suppressor grid of the input and the other for applying potentials to the suppressor grids of the output and ringing gate tubes, a line finder gate tube common to said lines controlled by energy applied to the dynodes, a multiple connection from the output of the line finder gate tube to the grids of said triodes, a connection from the plate of the input to the control grid of the output gate tube, a low' pass filter in the last-mentioned connection, a line selecting circuit comprising register and counter tubes variably operable in accordance with the designation of the called line, a ringing oscillator associated with said line selecting circuit and connected with the control grid of the ringing gate, time channel gate tubes controlled by the counters, and means operable upon the actuation of any time channel gate tube for ap-. plyin a potential to the multiple connection to the grids of the triodes.

12. In a telephone system, a pluralityrof lines, electronic switching means for establishing a two-way talking connection between a calling and a called line, electronic distributor means common to said lines for establishing time channels during which the switching means becomes efiective for a connection, electronic ringing means associated with the switching means and common to said lines, electronic means common to said lines for rendering the ringing means efiective upon the selection of the called line, and' electronic tripping means common to said lines for the ringing means operated when the called line answers.

DAVID H. RANSOM.

REFERENCES CI'TED The iollowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date' 2,263,369 Skillman NOV. 18, 1941 2,387,018 Harley Oct.16, 1945 2,406,165 Schroeder AugQ ZO, 1946 

